1.0 Field of Invention
This invention relates to contraceptive intrauterine devices (IUDs) and methods of preventing conception.
2.0 Description of the Related Art
Reproductive medicine is lagging in contraception technologies at a time when the world population is about to include the largest proportion of people of reproductive age ever. This invention introduces Nitinol thin film, a recent major advancement in material science and micro-electro-mechanic technology, to help resolve longstanding limitations in existing contraceptive intrauterine devices.
Intrauterine contraceptive devices (IUDs) are objects inserted into the uterus to prevent conception. Introducing an object into the uterus for birth control is an ancient discovery that has evolved to become the modern IUD. The use of such devices is based on the fact that the presence of a foreign object in the uterus discourages conception. IUDs have been invented of numerous and varied solid shapes and configurations. The most well known shapes are the ring, the “S”, the coil or spiral, the “T” and the “T” with its transversal arms bent down. These devices are configured to occupy a significant portion of the uterine fundus in order to prevent expulsion through the cervical os, a lumen of a few millimeters in diameter.
Existing IUDs are most commonly inserted using an insertion tube and a complementary plunger. Prior to insertion, the extended arms of the “T” are manually inserted into the upper end of the insertion tube The tube is of sufficient diameter and malleability to constrain the extended arms of the device in a folded position during insertion. The loaded tube is pushed through the cervical os into the uterine cavity. When the desired position is achieved, the tube is withdrawn to release the IUD while the inner plunger is manually held stationary. Withdrawal of the insertion tube allows the arms of the “T” to unfold inside the uterus.
The required manual placement of the IUD in the insertion tube is disadvantageous because it is cumbersome, time consuming, and increases the possibilities of compromising the sterile field. Moreover, where the IUD must be positioned by human manipulation, there exists a hazard of erroneous placement that could reduce contraceptive effectiveness and may be a source of injury to the patient. Approximately 1 in 500 insertions of existing rigid IUDs cause perforation.
IUDs of some configurations must be positioned in the insertion tube by drawing back on the “tail,” i.e., the string attached to the IUD for removal from the uterus. Such a method, however, is undesirable for an IUD having a “T” configuration since the arms would be drawn upwards. In some devices the folding of the IUD or placement in the insertion tube occurs after the initial placement of the insertion tube in the uterus, resulting in less control on placement position.
Attempts have been made to reduce the size of convention solid IUDs to allow use by younger women, but reducing size and surface area result in a less effective contraceptive and an increased rate of expulsion. The challenges in adapting these devices for use by nulliparous women include reducing size to reduce trauma and adverse reactions, while maintaining a large enough inert or medicated surface area to maximize effectiveness and a size sufficient to resist expulsion. These problems have limited the use of existing IUDs, especially in younger women.
The use of Nitinol is already well established in other areas of medicine and thin film devices are being developed to replace or expand these applications. For example, thin film devices are successfully used in neuro- and neurovascular surgery, where miniaturization, flexibility, and compliance are imperative to reach small vessels and to remove clots and block aneurisms.